Thanks. I was told the 3-56 could be used in place of the 2.5x.45 but it might be a little loose. My thought is I can't find a 2.5 and get a 3-56; could loctite (the brand that can be loosened if needed), be applied to the threads to sufficiently tighten the 3-56? I have been looking on Midway's website and it appears the 3-56 is a common size and they have the white beads that I am looking for. Also, they list the 3-56 together with the 2.5x.45; so it appears either size could be used. However, they don't list any such size as a 2.2x.45 or a 2-56 for the middle bead. What I an trying to do is install 2 ivory colored beads on my over/under barrels. Thanks again. Ed
I did exactly what you're talking about. Because the 3-56 is a smaller size the threads on the bead didn't fully seat in the tapped hole in the barrel. When I tightened it, the threads in the barrel stripped. I had to permanently glue it in with JB Weld.
dickgtax: Sorry for the confusion. I was trying to edit my last response when you inserted your input. Like I stated, Midway list a ton of front sights and even include the 2.5x.45 measurement with the 3-56 measurements on the same sights.
You folks are comparing 2.5 x .45 and 3-56 threads like they are the same thing. 2.5 is a metric thread. The proper designation would be M 2.5, or M6. You are comparing apples to oranges my friends. The numbers don't even refer to the same things. .45 refers to thread width while 56 refers to tpi. (threads per inch) Why would you want to loctite the wrong sight into your gun?
.45 in metric designation is the thread pitch - as in 0.45 mm / thread. There are 25.4 mm per inch. so converting the .45 to US ANSI thread designation is 25.4/0.45 = 56.44 threads per inch. The major diameter of 2.5 mm = 2.5/25.4 =0.0984" , the specs for a #3 screw major diameter range from a min of 0.0949 to 0.099" probably should check pitch diameters and tolerances - but i think a 3-56 and an m2.5 x .45 are very, very close.
pitch M2.5 = 2.117-2.188 or 0.0833" - 0.0861" ANSI pitch specs for a # 3 (2A) are 0.0845 - 0.0867 IOW very -very close. It would take a thread on the extreme edge of tolerance to not meet specs of either metric or US ANSI specs.
Mike & John: Thanks a lot. I just could not figure out exactly what I needed. I had a feeling that the 3-56 would work on the front sight; but I was totally unsure as to what the thread was for the middle bead. Thanks again. Ed